“The FBI’s failure to take action against this killer is unacceptable,” Scott said.

“Seventeen innocent people are dead and acknowledging a mistake isn’t going to cut it. An apology will never bring these 17 Floridians back to life or comfort the families who are in pain.”

A person close to Cruz contacted the FBI on Jan. 5 expressing concerns about the troubled teen’s “gun ownership, desire to kill people, erratic behavior and disturbing social media posts, as well as the potential of him conducting a school shooting,” the department said.

The call to the FBI’s official tip line should have been classified as a “potential threat to life” and forwarded to the FBI Miami Field Office.

“The information was not provided to the Miami Field Office, and no further investigation was conducted at that time,” it said in a statement.

Cruz, 19, went on to carry out a bloody rampage at Marjorie Stoneman Douglas High School on Wednesday — killing 17 people and wounding 14 others.

“Well, they made a big mistake, didn’t they?” fumed David Mizen. 55, whose 17-year-old son Lewis survived the massacre.

“Because of that, 17 people aren’t here.”

Lewis Mizen shook his head in disgust when he learned the news.

“That was a huge comment that the FBI missed,” said the senior student.

“He says he wants to be a professional school shooter. How a kid like him gets any kind of weapon is ridiculous.”

Attorney General Jeff Sessions said he ordered his deputy Rod Rosenstein to lead a probe into the FBI’s botched response.

“It is now clear that the warning signs were there and tips to the FBI were missed,” Sessions said.

“We see the tragic consequences of those failures.”

Wray also vowed to investigate what led to the massive misstep.

“We are still investigating the facts,” said FBI Director Christopher Wray.

“I am committed to getting to the bottom of what happened in this particular matter, as well as reviewing our processes for responding to information that we receive from the public.

“It’s up to all Americans to be vigilant, and when members of the public contact us with concerns, we must act properly and quickly.”

Wray acknowledged that the revelation will likely add a fresh layer of pain to the victims’ grieving families.

“We have spoken with the victims and families and deeply regret the additional pain this causes all those affected by this horrible tragedy,” he said.

The January tip wasn’t the first time someone tried to warn the FBI about Cruz.

A Mississippi bail bondsman alerted the feds last September to a disturbing YouTube comment left by a user named “Nikolas Cruz.”

The FBI immediately followed up with the man but the investigation ended after “database reviews” yielded no clues into the identity of the poster, officials said.

Florida Sen. Marco Rubio called the FBI’s failure to act on the tip “inexcusable.”

“The fact that the FBI is investigating this failure is not enough,” said for former GOP presidential contender.

“Both the House and Senate need to immediately initiate their own investigations into the FBI’s protocols for ensuring tips from the public about potential killers are followed through.”

Broward County Sheriff Scott Israel refused to pin blame on the feds.

“At the end of the day, make no mistake about it America, the only one to blame for this incident is the killer himself,” Israel said.

Cruz, who was mentally ill and obsessed with firearms and violence, confessed to the crime, authorities said.

He was being held under suicide watch at the county jail on 17 counts of premeditated murder.